Sum the values in Array

[DINESH BABU]

Hi, 

I am trying to sum values in array (list of variables) like below. But I don't know how to do it AMPL. Could anyone help me how to do it in AMPL? 

a = (1,2,3,4,5,6)

result = (1, 3, 6, 10, 15, 21)

Thanks,
Dinesh.

[Robert Fourer]

It is hard to say exactly what you should do, since you have not said how you want to define "a" and "result" in your AMPL model. But as an example, if you have defined "param a {1..6};" and "param result {1..6};" then you can write

let {i in 1..6} result[i] := sum {j in 1..i} a[j];

or

let {i in 1..6} result[i] := if i=1 then a[1] else result[i-1] + a[i];

These are just two ways of getting the same result.

Bob Fourer
am...@googlegroups.com

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[Dinesh Babu Seenivasan]

Hi Robert,

"a" is output and it's have list of parameters. Now I am doing this in Excel and I have attached it here. If you check it, you can understand what I am trying do it ampl.  

Thanks,
Dinesh.

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[Robert Fourer]

You might define in your AMPL model,

param N integer > 0;
param a {1..N};
param result {i in 1..N} = sum {j in 1..i} a[j];

and then in a data file, give AMPL data for param N and param a from the first column of your spreadsheet (as in this shortened example):

param N := 6;
param a :=
1 0
2 0.3571
3 0.35867
4 0.36026
5 0.36186
6 0.36347 ;

Then param result will contain the values from the second column of the spreadsheet.

Bob Fourer
am...@googlegroups.com

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[Dinesh Babu Seenivasan]

Hi Robert,

Thanks for your information. I will try and let you know!

Regards,

Dinesh.